Production of high quality jet fuels by two-stage hydrogenation



United States Patent 3,369,998 PRODUCTION OF HIGH QUALITY JET FUELS BYTWO-STAGE HYDROGENATIQN Paul G. Bercik, Glenshaw, Pa., and Leslie D.Moore, Lisle, Ill., assignors to Gulf Researchdz Development Company,Pittsburgh, Pa., a corporation of Delaware No Drawing. Filed Apr. 30,1965, Ser. No. 452,394

5 Claims. (Cl. 208-210) This invention relates to an improved processfor preparing a jet fuel, particularly a superior quality et el. Thedevelopment of jet engines has called for higher grade fuels. Thespecifications for such fuels for military uses are denominated lP-l,JP-3, JP-4, etc. They may be roughly classified as follows:

Detailed specifications for JP5 and JP6 fuels may be found in MIL-J-5624and MIL-J-25656.

For various special purposes, it is, of course, necessary to describeintermediate or more stringent requirements. It is, therefore, notsurprising that a certain tightening of specifications became necessarywhen lP-S jet fuel was required for use in Mach 2 jet engines.

A high speed jet aircraft builds up heat as it moves through theatmosphere. At sub-sonic speeds the heat can .be dissipated by aircooling the engine, But at the higher supersonic speeds, the heat buildsup faster than it can be dissipated to the air. The most convenientreservoir for this heat is the fuel and it has become common practice todissipate this excess in the fuel contained in aircraft fuel tanks.

Therefore, the fuel must be raised to relatively high temperatures.Unfortunately, the thermal stability of ordinary JP-S fuel was notsufficient for the heat load envisioned in the Mach 2 aircraft. At thetemperatures predicted, the fuel tended to form coke and other deposits.Therefore, modifications were made in the list of specifications.

Regular JP-5 specifications were required and in addition:

(1) A minimum of 35 smoke point.

.(2) A minimum of 7S luminometer number.

(3) A higher thermal stability defined by the following test:

in a standard CFR coker, the 400 F./500 F. test run at a fuel flow rateof 3 lbs, per hour is to result in a a maximum pressure drop of fiveinches of mercury and a maximum deposit rating of two in 300 minutes.

It is important that fuels burn cleanly in a jet engine.

Deposits caused by poorly burning fuels decrease the efficiency of thepower plant. Increased engine temperatures are caused by radiantheating. Fuels burningwith a luminous flame should also be avoidedbecause the additional heat produced by the emitted radiation seriouslydamages the engine burner walls and other vital engine parts. Frequentoverhaul is then necessary.

The smoke point of a fuel is a means of measuring its LII 3,309,098Patented 1F eh.a 20, 1968 ability to burn cleanly. It is determined by atest in which a sample is burned in an enclosed lamp. with a scale. Themaximum height that the flame reaches Without smoking is estimated. Thisnumber, in millimeters, is the smoke point. The test is described inASTM D1322-59t.

The luminosity of a fuel is a measurement of the radiation ofincandescent carbon particles obtained in the burning of that fuel. Itis determined by the burning of fuel in a luminometer lamp and measuringthe flame radiation with a photocell unit. The details of this test aredescribed in ASTM D1740-60t.

The high temperature stability of jet fuels is measured in the fuelcoker test which subjects the test fuel to temperatures and conditionssimilar to those occurring in aircraft engines. A fuel is pumped at acertain rate through a preheater which simulates hot fuel line sectionsof the engine. It then passes through a heat filter which representssmall fuel passages in the hot section of the engine. The extent of thebuild-up as measured by pressure drop across the filter, in combinationwith a visual assessment of the deposit condition of the preheater, isused as an evaluation of thermal stability.

It is an objective of this invention to provide improved procedure forthe manufacture of a high quality jet fuel.

It is a further object of this invention to provide procedure for themanufacture of a jet fuel meeting all JP5 and JP6 specifications.

It is also an object of this invention to provide procedure forproducing a fuel meeting JP-S specifications and in addition having aminimum smoke point of 35, a minimum luminometer number of and a higherthermal stability (defined by the following test: in a standard CFRcoker, the 400 F./ 500 F. test run at a fuel flow rate of 3 lbs. perhour is to result in a maximum pressure drop of five inches of mercuryand a maximum deposit rating of 2.0 in 300 minutes).

It is a further object of this invention to provide procedure formanufacture of a JP-S jet fuel suitable for Mach 2 jet engines.

It is a further object of this invention to provide for a 2-stephydrogenation of straight run kerosene.

Other objects will appear later herein.

These and other objects of the invention are achieved by treating astraight run kerosene with two successive catalytic hydrogenations atcarefully selected conditions with especially chosen catalysts. Thefirst step removes sulfur and nitrogen compounds from the kerosene andthe second step saturatively hydrogenates the resultant product.

This process may be used with any straight run kerosene. It has beendiscovered by applicants that cycle stocks are completely unsuitable asfeeds for this process. It may be possible under certain conditions tomanufacture a lower quality jet fuel by hydrogenation processesutilizing cycle oils. But it is not possible to manufacture the highquality jet fuel which is an objective of this invention. Included inthe specification of this fuel, as indicated above, is a requirement forhigh luminosity numbers. These are conferred by paraflins. Any cycleoil, with boiling point in the kerosene range, will have a high aromaticcontent. When such a cycle oil is hydrogenated, a product of highnaphthenic content is obtained. This product is marked by low luminositynumbers.

Any feed with an aromatic content higher than 50% would be competelyunacceptable for this process.

If it is desired to produce a JP6 fuel, a mixture of straight-runkerosene and naphthas may be used as a charge stock.

The charge stock is submitted to a finst hydrogenation stage in order toremove sulfur and nitrogen compounds. The temperature may be betweenabout 650 F. and 750 3 F., the pressure 500 and 1500 p.s.i.g., theliquid hourly space velocity 1.0 and 6.0. Temperatures greater than 750F. must not be used because undesirable, excessive hydrocracking andden-itrogenation will result. The hydrogen recircul-ation rate usuallywill vary from about 1,500 to 10,000 standar'd cubic feet per barrel.

The catalyst employed in this first stage hydrogenation may be any ofthe well-known hydrorefining catalysts em ployed for hydrogen treatmentof petroleum fractions for hydrodesulfurization, denitrogenation, etc.Such catalysts include metals, oxides and/or sulfides of Group VI (leftcolumn) or Group VIII. Metals of Group VI and Group VIII compounds arelikewise suitable. Specific examples of satisfactory catalysts includemolybdenum oxide or sulfide, tungsten oxide or sulfide, nickel oxide orsulfide, cobalt molybdate, nickel tungstate, etc. These catalysts areadvantageously deposited on inert porous carriers such as activatedalumina, gamma alumina, eta alumina, pseudo-boeh'mite alumina,silica-alumina cracking cat-alyst, etc. In the event that a carrier suchas the last-mentioned is employed, treating temperatures only up to 715F. can be used without excessive hy-drocracking. Between about 5 and 25%by weight of catalyst (determined as metals) is usually deposited onthese carriers.

In the second stage hydrogenation, temperatures from 450 F. to 700 F.may be used. However, above 650 F. a minor amount of hydrocracking mayoccur. This would tend to decrease the thermal stability of the jetfuel. Consequently, a temperature range of 450 to 630 F. generally givessuperior results. vPressure in the second hydrogenation stage may varyfrom 500 to 1500 p.s.i.g. or higher. It is especially worthwhile to makecertain that the pressure does not drop significantly below 500 p.s.i.g.in combination with temperatures in the higher portions of the rangesmentioned. Such a combination will result in reforming reactions whichresult in formation of aromatics and thus will severely curtail qualityand, to a lesser extent, yield of jet fuel. Space velocities from 1 tomay be used. A space velocity of from 1 to 5 is preferred. Hydrogen maybe circulated at the rate of between about 2,000 and 10,000 standardcubic feet per barrel.

The catalyst for the second hydrogenation may be either about '12 to 50%nickel, cobalt molybdenum, tungsten, or combinations of these on (gamma,eta, or pesudo-bochmite) alumina or on kieselguhr or about 0.5 to 5.0%noble metal such as platinum or palladium on the various above-describedaluminas.

The feed stock is contacted with the hydrogen and the catalyst in any ofthe customary manners for the hydrogen treatment or hydrocarbons. Apreferred procedure is to pass the hydrogen and vaporized hydrocarbontogether through a high pressure reactor which contains a bed of thehydrofining catalyst. The hydrogen and feed may be passed downwardly orupwardly through the reactor. After passage through the reactor, thehydrogen is separated from the condensed, hydrofined hydrocarbon. It isthen recycled to the reactor from which it was derived. A portion ofthis hydrogen is bled off and fresh or makeup hydrogen is added tomaintain hydrogen purity. While the hydrogen from the first stage may beused in the second stage, it must be treated to remove ammonia andhydrogen sulfide formed in the first stage by hydrogenation of nitrogencompounds. Otherwise, adequate hydrogenation in the second stage doesnot take place. Distillation of the product from the second stage isusually desirable since there are usually some products formed in one orboth stages which do not have the appropriate boiling point for thedesired jet fuel.

Example I A virgin kerosene of West Texas origin was hydrogenated over aPeter Spence catalyst comprising 2.1% cobalt and 8.7% molybdenumsupported on activated alumina. Reaction conditions were as follows:

4 Temperature F.) 665 Pressure (p.s.i.g.) 600 LSHV 4.2 Hydrogen flow(s.c.f./bbl.) 1700 The liquid hydrocarbon portion of the resultantproduct was saturatively hydrogenated over a prereduced, 10- 20 mesh 48%nickel on kieselguhr catalyst under the following reaction conditions:

Temperature F.) 525 Pressure (p.s.i.-g.) 1000 LSHV 1.0 Hydrogencirculation (s.c.f./bbl.) 8000 The specifications of the product fuelare set down in Table I. The specifications for the modified Mach 2 JP-5fuel are listed alongside.

TABLE I Specifications Prodfuct o Desired, Example Rigid but not I Rigid50% at F.)

at F.) Copper Strip Corrosion, ASTM Existent Gum, mg./ m1... FlashPoint, F

Net Heat Value, B.t.u./lb 2 18, 500 18, 700 Freezing Point, F 1 55 64Viscosity, cs. at -30 F. 1 16. 5 3 11.8 Sulfur, p.p.m l 1, 000 1. 0Mercaptan Sulfur, p.p.m 1 1 Luminorneter Number. 2 75 89 Smoke Point 235 42 Water Tolerance, ml 1 l Thermal Stability, ORG Coker:

Time, minutes 300 Fuel Flow, lb./hr 3 Preheater Temperature, F 400Filter Temperature, F- 1500 Pressure Drop, in. Hg 3. 3 Preheater Deposit0 1 Max. 2 Min. 3 At -40 F.

The jet fuel made by this process surpasses all the modified JP-Srequirements. The actual flash point was not measured but this propertycould be adjusted by distillation if necessary. The luminometer numberof 89 and the smoke point of 42 were much better than the minimumspecifications and indicative of clean flame burning, the fuel giving a3.3 in. Hg pressure drop and no preheater deposit passed the stabilityrequirements.

We claim:

1. The method of manufacturing a jet fuel which comprises contacting astraight-run kerosene with hydrogen in the presence of a hydrogenationcatalyst formed from at least one member selected from the groupconsisting of nickel, cobalt, molybdenum and tungsten and oxides andsulfides thereof, on an inert porous carrier, at a temperature of 650 to750 F., at a pressure of 500 to 1500 p.s.i.g. with a liquid hourly spacevelocity of 1.0 to 6.0 and a hydrogen circulation rate of 1,500 to10,000 standard cubic feet per barrel of kerosene, contacting theresultant product with hydrogen in the presence of a catalyst whichcomprises a metal selected from the group consisting of nickel, cobalt,tungsten, molybdenum and the noble metals, said catalyst being supportedon a porous refractory support selected from the group consisting ofalumina and kieselguhr, at a temperature of 450 to 700 F. at a pressureof 500 to 1500 p.s.i.g., a liquid hourly space velocity of 1.0 to 10.0and a hydrogen circulation rate of 2,000 to 10,000 standard cubic feetper barrel of said product of the first stage, the combination ofconditions being selected to produce a superior jet fuel having alurninometer number of at least 75.

2. The method of manufacturing a jet fuel which comprises contacting astraight-run kerosene with hydrogen in the presence of a hydrogenationcatalyst formed from at least one member selected from the groupconsisting of nickel, cobalt, molybdenum and tungsten and oxides andsulfides thereof, on an inert porous carrier at a temperature of 650 to750 F., at a pressure of 500 to 1500 p.s.i.g. with a liquid hourly spacevelocity of 1.0 to 6.0, and a hydrogen circulation rate of 1,500 to10,000 standard cubic feet per barrel of kerosene and cocurrentlycontacting the resultant product with hydrogen in the presence of acatalyst which comprises a metal selected from the group consisting ofnickel, cobalt, tungsten, molybdenum and the noble metals, said catalystsupported on a porous refractory support selected from the groupconsisting of alumina and kieselguhr at a temperature of 450 to 630 F.at a pressure of 500 to 1500 p.s.i.g., a liquid hourly space velocity of1.0 to 5.0 and a hydrogen circulation rate of 2,000 to 10,000 standardcubic feet per barrel of said product of the first stage, thecombination of conditions being selected to produce a superior jet fuelhaving a luminometer number of at least 75.

3. The method of manufacturing a jet fuel which comprises contacting astraight-run kerosene with hydrogen in the presence of acobalt-molybdenum catalyst at a temperature of 650 to 750 F., at apressure of 500 to 1500 p.s.i.g. with a liquid hourly space velocity of1.0 to 6.0, and a hydrogen circulation rate of 1,500 to 10,000 standardcubic feet per barrel of kerosene and contacting the resultant productwith hydrogen in the presence of a catalyst comprising a metal selectedfrom the group consisting of nickel, cobalt, tungsten, molybdenum andthe noble metals, said catalyst supported on a porous refractory supportselected from the group consisting of alumina and kieselguhr at atemperature of 450 to 630 F. at a pressure of 500 to 1500 p.s.i.g., aliquid hourly space velocity of 1.0 to 5.0 and a hydrogen circulationrate of 2,000 to 10,000 standard cubic feet per barrel of said productof the first stage, the combination of conditions being selected toproduce a superior jet fuel having a luminometer number of at least 75.

4. The method set forth in claim 3 wherein the second stage catalystcomprises nickel.

5. The method set forth in claim 1 wherein the second stage catalyst is12 to percent nickel on kieselguhr.

References Cited UNITED STATES PATENTS 3,077,733 2/1963 Axe et al.260667 3,147,210 9/1964 Hass et al. 260667 3,201,342 8/1965 Bachman etal. 260-667 3,236,764 2/1966 Den Herder et al. 260-667 3,304,338 2/1967Parish 260-667 SAMUEL P. JONES, Primary Examiner.

DELBERT E. GANTZ, Examiner.

1. THE METHOD OF MANUFACTURING A JET FUEL WHICH COMPRISES CONTACTING A STRAIGHT-RUN KEROSENE WITH HYDROGEN IN THE PRESENCE OF A HYDROGENATION CATALYST FORMED FROM AT LEAST ONE MEMBER SELECTED FROM THE GROUP CONSISTING OF NICKEL, COBLAT, MOLYHBDENUM AND TUNGSTEN AND OXIDES AND SULFIDES THEREOF, ON AN INERT POROUS CARRIER, AT A TEMPERATURE OF 650 TO 750*F., AT A PRESSURE OF 500 TO 1500 P.S.I.G. WITH A LIQUID HOURLY SPACE VELOCITY OF 1.0 TO 6.0 AND A HYDROGEN CIRCULATION RATE OF 1,500 TO 10,000 STANDARD CUBIC FEET PER BARREL OF KEROSENE, CONTACTING THE RESULTANT PRODUCT WITH HYDROGEN IN THE PRESENCE OF A CATALYST WHICH COMPRISES A METAL SELECTED FROM THE GROUP CONSISTING OF NICKEL, COBALT, TUNGSTEN, MOLYBDENUM AND THE NOBLE METALS, SAID CATALYST BEING SUPPORTED ON A POROUS REFRACTORY SUPPORT SELECTED FROM THE GROUP CONSISTING OF ALUMINA AND KIESELGUHR, AT A TEMPERATURE OF 450 TO 750*F. AT A PRESSURE OF 500 TO 1500 P.S.I.G., A LIQUID HOURLY SPACE VELOCITY OF 1.0 TO 10.0 AND A HYDROGEN CIRCULATION RATE OF 2,000 TO 10,000 STANDARD CUBIC FEED PER BARREL OF SAID PRODUCT OF THE FIRST STAGE, THE COMBINATION OF CONDITIONS BEING SELECTED TO PRODUCE A SUPERIOR JET FUEL HAVING A LUMINOMETER NUMBER OF AT LEAST
 75. 